Messages in this thread | | | Date | Mon, 2 Nov 2020 08:53:41 -0500 | From | Phil Auld <> | Subject | Re: [PATCH] sched/fair: remove the spin_lock operations |
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On Fri, Oct 30, 2020 at 10:16:29PM +0000 David Laight wrote: > From: Benjamin Segall > > Sent: 30 October 2020 18:48 > > > > Hui Su <sh_def@163.com> writes: > > > > > Since 'ab93a4bc955b ("sched/fair: Remove > > > distribute_running fromCFS bandwidth")',there is > > > nothing to protect between raw_spin_lock_irqsave/store() > > > in do_sched_cfs_slack_timer(). > > > > > > So remove it. > > > > Reviewed-by: Ben Segall <bsegall@google.com> > > > > (I might nitpick the subject to be clear that it should be trivial > > because the lock area is empty, or call them dead or something, but it's > > not all that important) > > I don't know about this case, but a lock+unlock can be used > to ensure that nothing else holds the lock when acquiring > the lock requires another lock be held. > > So if the normal sequence is: > lock(table) > # lookup item > lock(item) > unlock(table) > .... > unlock(item) > > Then it can make sense to do: > lock(table) > lock(item) > unlock(item) > .... > unlock(table) > > although that ought to deserve a comment. >
Nah, this one used to be like this :
raw_spin_lock_irqsave(&cfs_b->lock, flags); lsub_positive(&cfs_b->runtime, runtime); cfs_b->distribute_running = 0; raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
It's just a leftover. I agree that if it was there for some other purpose that it would really need a comment. In this case, it's an artifact of patch-based development I think.
Cheers, Phil
> avid > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
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